1. Statement of the Technical Field
The inventive arrangements relate generally to the field of capacitors, and more particularly to capacitors incorporated onto substrate materials.
2. Description of the Related Art
Physical dimensions continue to shrink and frequencies continue to increase in modern electronic circuits. Notably, there is a strong demand for smaller, lighter, and higher performance electronic devices. Several factors currently limit the extent to which the size and weight of electronic devices can be reduced and the performance can be increased. In particular, the relatively low energy storage density of conventional capacitors is a limiting factor.
Electrical characteristics of conventional capacitors, such as dissipation factor (DF), equivalent series resistance (ESR), leakage resistance, equivalent series inductance (ESL), dielectric absorption, and dielectric breakdown, are limiting factors to filter performance as well. For example, DF, ESR, ESL, and dielectric absorption each negatively effect a capacitors ability to pass or shunt RF signals with minimum attenuation and distortion.
Moreover, it is well known that conventional capacitors are prone to failure due to dielectric breakdown when the capacitors are exposed to an electromagnetic pulse (EMP) or high energy voltage spikes. This flaw is of particular concern when a capacitor is being used in a mission critical system, such as a power supply in a satellite or an aircraft, or an RF filter in military hardware or a secure facility. Accordingly, there exists a need for a high performance capacitor that provides high energy density and good RF performance, and that is rugged enough to withstand EMP""s and voltage spikes that are of concern in high reliability environments.
The present invention relates to a method for filtering an electrical signal. The invention includes the steps of rotating a conductive disc about an axis, applying a magnetic field to the conductive disc in a direction that is generally parallel to the axis of rotation, electrically connecting a first and second conductor to the disc at radially spaced locations thereon, and connecting the first and second conductors in at least one of a series and parallel configuration. The conductive disc can be formed in a recess in a substrate, which can have a printed circuit or an integrated circuit. The substrate can consist of a semiconductor or ceramic, such as a low temperature co-fired ceramic.
Notably, the first and second conductors and the conductive disc rotating in the magnetic field can define an electromechanical capacitor, which can be used for capacitively filtering a signal. Further, the first and second conductors can be connected to an inductor in a series or a parallel configuration to form a filter circuit, for example a low pass filter circuit, a band pass filter circuit, and high pass filter circuit, and band notch filter circuit and an all pass filter circuit. Moreover, a second electro-mechanical capacitor can be connected to the first electro-mechanical capacitor in a series or parallel configuration to control a filter response. Importantly, the intensity of the magnetic field can be varied in response to a control signal to produce a desired filter response for filtering a signal. Further, the thickness or mass density of the conductive disc also can be selected to produce a desired filter response.